SPP1 and atrial fibrillation: Figure 3b shows optical images of the adipogenic (Oil Red O staining), osteogenic (von Kossa staining), and chondrogenic (Alcian Blue) differentiation of AF-MSCs in the presence or absence of Nanog overexpression, as well as expression of markers specific to adipogenesis (aP2 and PPARγ2) (Fig. 3c), osteogenesis (osteopontin and osteocalcin) (Fig. 3d), and chondrogenesis (Collagen II and Aggrecan) (Fig. 3e) in AF-MSCs and AF-N-MSCs.